Camshaft phasers for varying the phase relationship between the crankshaft and a camshaft of an internal combustion engine are well known. A prior art vane-type phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is supplied via a multiport oil control valve (OCV), in accordance with an engine control module, to either the advance or retard chambers as required to meet current or anticipated engine operating conditions.
In a typical prior art vane-type cam phaser, the tip of each rotor vane and stator lobe is provided with a compressible seal element for wiping the cylindrical wall of the opposite member to prevent leakage between the advance and retard chambers.
A first known wiper seal element utilizes a two-piece construction consisting of a plastic wiper blade and backing spring disposed within the vane or lobe to load the wiper blade against the stator or rotor surface.
A second known wiper seal element utilizes a two-piece seal disposed in an axially-extending groove formed in the vane or lobe tip. Typically, an elastomeric spring is overmolded onto a rigid plastic wiper-shaped substrate. This configuration requires two successive manufacturing steps and two different materials to provide a single wiper element, creating undesired manufacturing cost and complexity.
Many prior art wiper configurations also require significant tolerance control on the dimensions of the groove in which the wiper element is disposed. The depth of the groove can affect the spring force on the wiper element, and the width of the groove can affect control of oil leakage behind the wiper element.
What is needed in the art is an improved wiper seal element that is simple and inexpensive to manufacture, is of one-piece construction, is durable, and is self actuating to urge itself continuously against a stator or rotor wall.
What is further needed in the art is an improved wiper seal system that is tolerant of manufacturing variability in the depth and width of a groove in the tip of a rotor vane or stator lobe.
It is a principal object of the present invention to improve the reliability of a wiper seal element in a vane-type camshaft phaser.
It is a further object of the present invention to reduce the manufacturing cost and complexity of a phaser wiper seal element.
It is a still further object of the present invention to reduce the manufacturing cost and complexity of forming a tip groove by relaxing the width and depth tolerances required of the groove to seal the phaser against leakage between the advance and retard chambers.